The present invention relates to a rolling bearing with a sealing device, which is used for constituting a rotary supporting portion which may be splashed with muddy water or the like, such as a wheel supporting portion of an automobile.
A rolling bearing which constitutes a wheel supporting portion of an automobile is required to have a high sealing performance in order to prevent muddy water splashing when the automobile runs, from entering the supporting portion. Conventionally, therefore, a pair of seal rings are disposed in an open end portion of such a rolling bearing so as to configure a double sealing structure, thereby blocking the ingress of muddy water into the rolling bearing. FIG. 3 shows an example of the structure of a prior art rolling bearing with a sealing device which is configured in consideration of such circumstances.
A plurality of balls 5 functioning as rolling elements are disposed between an outer raceway 2 formed in the inner peripheral face of an outer race 1 and an inner raceway 4 formed in the outer peripheral face of a shaft 3 which is a member equivalent to an inner race, thereby enabling the outer race 1 and the shaft 3 to be relatively rotated. A pair of seal rings 6a and 6b are disposed between the inner peripheral face of an end portion of the outer race 1 and the outer peripheral face of an end portion of the shaft 3 so as to be arranged in series in the axial direction (the lateral direction in FIG. 3) of the outer race 1 and the shaft 3, thereby constituting a sealing device 7. The seal rings 6a and 6b are formed into a circular ring-like shape with circular ring-like metal core members 8a and 8b, and elastic members 9a and 9b such as rubber or elastomer reinforced by the metal core members 8a and 8b, respectively.
Among the pair of seal rings 6a and 6b, the first seal ring 6a is disposed in the outer side in the axial direction (the outer side is the side opposing the space outside the rolling bearing, and in the right side of each of the figures) and opposes the external space. The inner peripheral edge of the elastic member 9a constituting the first seal ring 6a is engaged with an engaging groove 10a formed in the outer peripheral face of an end portion of the shaft 3, and the outer peripheral edge slidingly contacts with the inner peripheral face of the outer race 1. The second seal ring 6b is disposed in the inner side in the axial direction (the inner side is the side opposing the rolling elements constituting the rolling bearing, and in the left side of each of the figures) and between the first seal ring 6a and the plural balls 5. The outer peripheral edge of the elastic member 9b constituting the second seal ring 6b is engaged with an engaging groove 10b formed in the inner peripheral face of an end portion of the outer race 1. Two seal lips 11a and 11b are formed on the elastic member 9b. The tip end edge of one seal lip 11a slidingly contacts with the outer peripheral face of the end portion of the shaft 3, and that of the other seal lip 11b slidingly contacts with the inner side face of the metal core member 8a constituting the first seal ring 6a.
In the thus configured prior art rolling bearing with a sealing device, three sliding contact portions shown in (1) to (3) below exist between the external space and the space where the balls 5 are disposed, so as to be arranged in series with respect to the ingress path of muddy water and the like:
(1) the outer peripheral edge of the elastic member 9a and the inner peripheral face of the end portion of the outer race 1; PA0 (2) the tip end edge of the seal lip 11b and the inner side face of the metal core member 8a; and PA0 (3) the tip end edge of the seal lip 11a and the outer peripheral face of the end portion of the shaft 3.
Therefore, foreign substances such as muddy water existing in the external space hardly reach the space where the balls 5 are disposed.
In the prior art structure shown in FIG. 3, the engagement portion between the engaging groove 10a formed in the outer peripheral face of the shaft 3 and the inner peripheral edge of the first seal ring 6a, and that between the engaging groove 10b formed in the inner peripheral face of the outer race 1 and the second seal ring 6b do not have a sufficiently large engagement strength. As the outer race 1 and the shaft 3 are relatively rotated, therefore, the first and second seal rings 6a and 6b may be rotated with respect to the shaft 3 or the outer race 1, or deviated in the axial direction of the shaft 3 and the outer race 1.
The rotation of the first and second seal rings 6a and 6b with respect to the shaft 3 or the outer race 1 leads to the reduction of the sealing performance in each of the engagement portions. The deviation of the first and second seal rings 6a and 6b in the axial direction of the shaft 3 and the outer race 1 results in the reduction of the sealing performance in each of the sliding contact portions between the tip end edges of the seal lips constituting the seal rings 6a and 6b and the respective counter faces.